The strand formed during continuous casting has a tendency to stick to the mold. In order to avoid this, the mold is oscillated.
Various types of oscillators are in use. The simplest and most versatile is the so-called "short lever oscillator". With this oscillator, the speed of the mold varies sinusoidally. The sinusoidal speed variation presents a problem during the stroke in which the mold travels concurrently with the strand. Thus, the process of stripping the strand from the mold takes place only during the minor portion of this stroke in which the speed of the mold is greater than the casting speed, i.e., the speed of the strand.
The four eccentric oscillator produces a motion similar to that of the short lever oscillator and leads to the same problem.
Many attempts have been made to develop an oscillatory movement with a better stripping action. One result of these attempts is the cam follower oscillator which causes the mold to move at a relatively constant speed in excess of the casting speed during the major portion of the stroke in which the mold travels concurrently with the strand. However, the cam follower oscillator is extremely complex, requires a large amount of maintenance and is very sensitive to contamination and wear.
The hydraulically driven oscillator is likewise capable of moving the mold in excess of the casting speed during the major portion of the stroke in which the mold travels concurrently with the strand. This oscillator again requires considerable maintenance. Moreover, the controls are complex and subject to wear.